Can I copy tokens from one PDF to another?

[daijun]

Dears,
I just try to directly copy tokens from one pdf to another.  The program run 
with no error. But when I open the generated pdf, it shows error. 
Could anyone be kind help me?  Thank you. 


Code like:
PDDocument document2 = new PDDocument();  // target
PDPage newPage = new PDPage(); // new page in the target 
document2.addPage( newPage );



PDDocument document1 = PDDocument.load("c:\\a.pdf"); //source
PDDocumentCatalog catalog = document.getDocumentCatalog();
PDPage page = (PDPage) catalog.getAllPages().get(0);
PDFStreamParser parser = new PDFStreamParser(page.getContents());
parser.parse();
List tokens = parser.getTokens();

List newTokens = new ArrayList();
for(int j=0; j<tokens.size(); j++) {
                        Object token = tokens.get( j );
                        newTokens.add( token );
}                   



PDStream newContents = new PDStream(document2 );
ContentStreamWriter writer = new ContentStreamWriter( 
newContents.createOutputStream() );
writer.writeTokens( newTokens );
newContents.addCompression();

newPage.setContents(newContents);


document2.save("c:\\new.pdf");